using System;

​

public class Program

{

    public static void Main()

    {

        int input = 0;

        do

        {

            Console.Write("Please enter a number: ");

            string number = Console.ReadLine();

            if (int.TryParse(number, out input))

            {

                if (input < 3)

                {

                    Console.WriteLine("Number must be greater than 3 please");

                }

            }

        }while (input <= 3);

          for (int i = 3; i <= input; i+=3)

        {

            Console.WriteLine(i);

        }

​

    }

} 

​

//got tutored by the same guy on IRC. I also looked at the sorce code you provided us.